Hidden Treasures

April 27, 2021

Jo Wicht

Who would have thought that some of the most boring looking mineral specimens could be the most spectacular under shortwave fluorescent light? Look at these three, for example…

 

 

 

Over time I have made a point of collecting specimens if I am aware that they fluoresce because that is fun, but often one acquires others unknowingly. Because I agreed to take some photos to supplement this edition of the MinChat, I shone my UV light over my entire mineral collection to see what I could put together. I was very surprised, and have filled up far more space than anticipated.

Above, from the top(2), we have bultfonteinite and olmeite from KMF. I think I was collecting KMF minerals at the time and chose it because that name sounded different. Its photo below certainly looks different under shortwave light. The next are two minerals I was given. The middle(2), danburite covered in calcite from Mexico and colemanite from Turkey - again none have any colour when seen in daylight. Then the last(2) is a Tsumeb cerussite on matrix that came in a collection I bought from a friend when I was first interested in minerals. Only this week did I find it glowed that marvellous red. 

What else did I find in my cabinet? A small chunk of Nevada opal (top 2) in my rejects’ drawer; Joey von Borstel once gave me that. A Moroccan with barite and cerussite on galena (middle 2), and a very scruffy little piece of apatite and fluorite from Krantzberg Mine in the Erongo region (bottom 2). The reaction from the opal was particularly surprising.

 

 

 

Below is a Moroccan yellow fluorite on red quartz

 

As well as zircons above, and Tsumeb calcites below…

 

 

Hyalite opal from the Erongo region on quartz above left, and again on schorl with aquamarine below.

 

 

And chalcedony on an unknown matrix with tiny clear crystals also from the Erongo region …

 

Followed by a specimen from Rosh Pinah of galena on barite, seen from both sides.

 

 

From nearby Scorpion mine, (below) the fluorescence is quite different. Hemimorphite, tarbuttite and fluorapatite are found here.

 

 

Below is my most colourful specimen, which was hand-collected at Omehani fluorite mine dumps during the first Uis Gemboree in 2008. I have shown both sides of it.

 

 

AND FINALLY, here is my specimen of willemite from Berg Aukas which fluoresces and phosphoresces – the latter being the fact that it carries on glowing after the UV light has been switched off.

 



For this exercise the natural light photos were taken with a flash indoors under an overhead light against a black background and with the camera set on Auto. For the UV photos the overhead light was switched off, my camera was on the Twilight setting, and my Spectrolite MinMax UV lamp was set on shortwave.  JW 

By the way, some parrots fluoresce in patches. Anyone got a friend with a parrot? Reference, to prove that I am not making this up: Parker, A. 2005. Seven deadly colours: 166-7; 171-5; 172; 178-84. London: The Free Press (Simon & Schuster.) DM 

FUN FLUORESCENCE LINK

This is a nice fluorescent specimen: check out the different views for LW and SW fluorescence, and an example of phosphorescence. https://www.mineralauctions.com/items/sodalite-var-hackmanite-with-richterite-82784

 

 

DISTINGUISHING RUBY FROM GARNET AND RED GLASS USING FLUORESCENCE

April 26, 2021

Duncan Miller

Cut rubies, red garnets and red glass can look very similar. There are several techniques that can be used to determine if a red stone is a ruby. These include a semi-destructive relative hardness test (ruby will scratch garnet and glass, but not the other way around); using a polariscope to test for birefringence (ruby is birefringent whereas glass and most garnet are not); and using a dichroscope to see the two pleochroic shades of red in ruby (which are absent in garnet and ...


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Feldspar, or so I thought….

April 26, 2021

Willie Lombard

I collect different species of minerals and rocks of SA and Namibia and need only one good example of each. Right across from the old Swanson Enterprises building in Springbok is an open yard with some large heaps of rocks and minerals. I asked the resident on the property if I could have a look-around. No problem. Found some fluorites and a good example of a diorite. There were some feldspars and a lot of pegmatites. I was sleeping over, so I asked the resident if I could ret...


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Yooperlites of Pilanesberg

April 26, 2021

Willie Lombard

On the shores of Lake Superior in the USA a fluorescent rock made headlines (on YouTube, anyway!). They call the normally drab rock a Yooper, after the locals from Upper Michigan. A geologist from the local university found that the sodalite in the rock causes the yellow fluorescence. I wish my sodalite would fluoresce like that! Those that do, produce only a very weak yellowish glow.


On my way to the Groot Marico Gemboree in 2018 I decided to sleep over in the Pi...


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FLUORESCENCE IN MINERALS: A BRIEF INTRODUCTION TO WONDERLAND

April 26, 2021

By Peter Rosewarne

Introduction

The branch of mineralogy dealing with fluorescence apparently gained popularity in the 1930s with the availability of battery-powered portable ultraviolet (UV) lamps. The pioneer in producing such UV lamps and using them to prospect for and showcase minerals was Thomas S Warren, after whom the Thomas S Warren Museum of Fluorescence at Sterling Hill Mine Museum in the USA is named.

Those of you who have been paying attention to previous MinChat articles will ...


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TRIALS AND TRIBULATIONS WITH CUT GEMSTONE HEATING

March 25, 2021
Duncan Miller

Inspired by the dramatic change in colour of the large tourmaline illustrated in last month’s Mineralogical Chatter, that went from autumn brown to a purplish-pink on heating by the client for whom I had cut it, I decided to experiment myself. A friend lent me a small ‘enamelling’ kiln; I bought a suitable crucible from jewellers’ supplier Lipman & Son in Cape Town (https://lipmanson.co.za/); and Ian Lipman generously gave me jewellery casting investment powder to protect...


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Six of the Best Specimens in the Mineral Kingdom!

March 25, 2021

By Peter Rosewarne

Introduction

Have you ever wondered if there was a specimen out there that was the world’s best, or what the best six or ten mineral specimens ever discovered are considered to be? I thought it might be a bit of fun to put together a “Six of the Best” of the mineral kingdom based on expert opinion in respected publications, such as The Mineral Record and its supplements, Masterpieces of the Mineral Kingdom, and American Mineral Treasures. Some of these discoveries g...


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THE MOST DIFFICULT JIGSAW PUZZLE OF ALL TIME

February 24, 2021
by
Duncan Miller

Imagine a jigsaw puzzle the size of the Earth, with most of the pieces missing. And those that aren’t missing are moving around all the time. This is the task that confronts some ambitious geologists. It is important because it explains why there are oceans and mountain chains, and why we may find rocks of similar ages and composition on far-flung continents. It also satisfies human scientific curiosity, and keeps some people employed and off the streets.

Until the mid-1960s...


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Botryoidal Minerals: A Colourful Trip Around the Mineral Kingdom

February 24, 2021

by
Peter Rosewarne

Introduction

My previous MinChat article on fluorite described a colourful trip around the world. In this article we take a colourful trip around the mineral kingdom, using minerals with a botryoidal habit as the guide. The idea came from the supplement to The Mineral Record of January-February 2020 on Mineral Collectors in Arizona, with the focus of one of the collectors being on botryoidal mineral specimens. The term botryoidal is derived from the Greek word botryios or ...


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FLUORITE - A COLOURFUL JOURNEY AROUND THE WORLD

January 15, 2021

by Peter Rosewarne

Fluorite: cubic, common, cheap (comparatively, but can be costly), contains calcium, and colourful, are some of the "C" words that can be used to describe this mineral. While good specimens of fluorite from classic localities aren’t cheap, most are cheaper than good specimens of ‘higher-end’ minerals such as azurite, dioptase, tourmaline and beryl and it is possible to build up a good collection of fluorites from worldwide localities. You are also likely to get a nice-...


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